Metallic wires are widely used in medical procedures, a common example being the guidewires used to locate intravascular devices such as angioplasty catheters. Conventional processes for forming such wires often include the step of cutting the components of the guidewire with diagonal pliers or the like. However, the cut end often exhibits sharp artifacts or burrs. This sharp edge can damage other materials or components used in conjunction with the wire. For example, the relatively soft polymeric materials of an angioplasty catheter could be easily damaged by such a burr or sharp edge. Likewise, the sharp edge also poses risk to personnel handling the wire or to the patient undergoing the medical procedure. Conventional means of removing these sharp edges include sanding the cut end. This process often produces undesirable microscopic grooves in the wire, leaves abrasive debris and raises manufacturing costs since it is time consuming and labor intensive and uses consumables.
Additionally, wires used in medical devices are often welded to attach another component to the wire end. For example, to add stiffness to the distal portion of a catheter, a hypotube can be welded to the end of a wire and positioned in the distal end of the catheter. However, the welding process often has the effect of removing material from the wire adjacent the welding area. Removal of material, or undercutting, in the weld area leads to decreased strength or altered bending properties and can lead to failure of the wire.
Accordingly, there is a need for improved wire forming processes that produce a non-traumatic cut end. There is also a need for wire forming processes that facilitate the welding of an additional component to the cut end of the wire. There is a similar need for wires that embody these features and a fixture for carrying out the processes.
The invention is directed to a process for forming a wire for use in a medical or intracorporeal device including cutting the wire to form a cut end and smoothing the cut end by heating the cut end to form a body of molten material which is cooled to solidify into a smoothed end. Heating the cut end can be achieved by applying laser energy. Any suitable type of laser energy may be used, delivered in pulses or in a continuous wave (CW) mode.
The invention is also directed to a process for forming a wire for use in an intracorporeal or medical device which is to be welded to an additional component. The process can include cutting the wire to form a cut end and forming a smoothed ball end at the cut end by heating the cut end to form a ball of molten material which is cooled so as to solidify. Again, heating the cut end of the wire can be achieved by applying laser energy. The process may also include abrading the cut end to reduce energy reflection prior to heating the cut end, particularly when laser energy is used.
The invention is also directed to a wire for use in a medical procedure or as a component in a medical device, the wire having a smoothed end formed by the process discussed above. Additionally, the invention is directed to a wire to be welded to an additional component with the wire having a smoothed ball end formed by the appropriate process described above. In one embodiment, a process having features of the invention can be carried out with a fixture for heating the end of a wire. The fixture can have a wire guide for accepting and clamping the wire in a desired position having a discharge axis, a source of heating energy having a focal point coaxially aligned with the discharge axis of the wire guide, and a removable stop that locates the end of the wire at the focal point of the source of heating energy.